Modeling of Semiconductor Substrates for RF Applications: Part I-Static and Dynamic Physics of Carriers and Traps

• Published in: IEEE transactions on electron devices Vol. 68; no. 9; pp. 4598 - 4605
• Main Authors: Rack, M., Allibert, F., Raskin, J.-P.
• Format: Journal Article
• Language: English
• Published: New York IEEE 01.09.2021; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Amplitudes; Carrier density; Carrier dynamics; Charge carrier density; Conductivity; coplanar waveguide (CPW) line; Current carriers; effective resistivity; Electrical resistivity; Electron traps; Excitation; Fermi-level pinning; Harmonic distortion; harmonic distortion (HD); Interfacial properties; large-signal modeling; Metal oxide semiconductors; MOS capacitors; nonequilibrium; Occupancy; Physical properties; pulsed MOS; Radio frequency; RF loss; RF substrate; Semiconductor materials; Silicon-on-insulator; Step functions; Substrates; TCAD modeling; trap-rich (TR) silicon-on-insulator (SOI); Trapped charge
• ISSN: 0018-9383; 1557-9646
• DOI: 10.1109/TED.2021.3096777

This article aims to provide deep insight into the physics of substrates for RF applications under large-amplitude signal excitations. The impact of physical parameters on substrate-induced harmonic distortion is modeled and well understood, from a theoretical and quantitative standpoint. This article formulates the interplay between applied voltage signal (dc or RF), interface fixed charge, and trapped charge in a charge-balance analysis for high-resistivity and trap-rich (TR) substrates. A TCAD approach gives strong insight into the impact of such semiconductor material and interface properties on the RF substrate's effective resistivity and linearity. First, a static analysis reveals how TR interface passivation overcomes the parasitic surface conduction effect using the concept of deep Fermi-level pinning. Next, substrates are analyzed in response to dynamic excitation signals. Using step functions to pulse an MOS structure from strong negative to strong positive applied charge sheds light on carrier dynamics. The characteristic time constants associated with variations in trap occupancy and in free carrier densities are discussed. Finally, sinusoidal large-amplitude signals are considered to analyze harmonic distortion from several types of substrates at various RF frequencies.